VRF-Aware H.323 and SIP for Voice Gateways

First Published: December 22, 2006, OL-11379-01

VPN routing and forwarding (VRF) divides a physical router into multiple logical routers, each having its own set of interfaces and routing and forwarding tables. Adding VRF-awareness to voice gateways allows a voice gateway to exist in the same router as a customer edge (CE) or provider edge (PE) WAN router.

The VRF-Aware H.323 and SIP for Voice Gateways feature adds single voice VRF support to session-initiated protocol (SIP), H.323, and IP-to-IP gateways and to Cisco Survivable Remote Site Telephony (Cisco SRST) routers.

Finding Feature Information in This Module

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•Call that involve transcoding, including both internal and external transcoders.

•SIP calls support both TCP and UDP signaling. However, for H.323 calls, only TCP is supported. H.323 UDP signaling is not supported.

The following features are not supported by VRF-aware H.323 and SIP:

•Call-fallback and RSVP features.

•H.323 Annex E calls.

•AAA and DNS components in voice-capable access routers. These routers communicate with AAA and DNS using the default routing table.

Information About VRF-Aware H.323 and SIP

Typically, service providers use a VRF between PE and CE routers to provide VPN support for customers. VRF is also used to segment data and voice traffic for improved traffic management, and VRF can be configured on an interface to process incoming packets according to the assigned VRF.

By configuring VRF-awareness on voice gateways you can specify a VRF for the voice traffic that is generated from within the gateway. The voice VRF is added to the VoIP service provider interface (SPI) of the gateway to send and receive signaling and media packets in the configured VRF. The SPI can send signaling and media packets only in the configured VRF, and receive signaling and media packets only from the configured VRF.

How to Configure VRF-Aware H.323 and SIP for Voice Gateways

To configure a voice VRF, you must shut down voice services on the gateway, assign a previously defined VPN VRF to the VoIP SPI, and then restart voice services.

This section describes the tasks required to configure VRF-aware H.323 and SIP for voice gateways.

Note If a voice VRF is not configured, signaling and media packets are sent using the default routing table.

Prerequisites

Be sure to check the following prerequisites before configuring a voice VRF:

•To ensure there are no active calls on the voice gateway during a VRF change, you must shut down the voice gateway before you configure or make changes to a voice VRF.

•If your configuration uses address binding, use the h323-gateway voip bind srcaddrip-address command to bind the gateway to an interface that belongs to the voice VRF.

•If the voice gateway configuration has H.323 RAS enabled, use the h323-gateway voip interface command to configure RAS on the interface that belongs to the voice VRF.

Restrictions

Restrictions for configuring VRF-aware H.323 and SIP are as follows:

•If the voice gateway configuration has H.323 RAS enabled, the gatekeeper must be accessible to the gateway in the configured voice VRF.

•When voice VRF is configured, the H.323 gateway and gatekeeper cannot communicate with each other if they are running on same router.

Voice VRF supports only the following call types:

•A single VRF for SIP-to-SIP calls

•A single VRF for H323-to-SIP calls

•A single VRF for H323-to-H323 calls

•A single VRF in IP-to-IP gateway call with a gatekeeper involved, but the gatekeeper is not on the same router.

RFCs

RFC

Title

No new or modified RFCs are supported, and support for existing RFCs has not been modified.

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Feature Information for VRF-Aware H.323 and SIP

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 1 Feature Information for VRF-Aware H.323 and SIP

Feature Name

Releases

Feature Information

VRF-Aware H.323 and SIP

12.4(11)XJ

12.4(15)T

VRF awareness in voice stack of H.323 and SIP enables voice in TDM gateways and Session Border Controllers (SBC) to be in its own single VRF in VRF-lite and MPLS networks. Cisco SIP SRST is also available for the phones that are in the voice VRF.

Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.